In recent years, various types of information such as image and data in addition to speech are targeted in radio communication, particularly in mobile communication. With this trend, there is a growing demand for high reliability and high speed transmission. However, when high speed transmission is performed in mobile communication, influences of delay signals due to multipath transmission cannot be ignored, and the transmission performances deteriorate due to frequency selective fading.
Multicarrier communication represented by an OFDM (Orthogonal Frequency Division Multiplexing) scheme is becoming a focus of attention as one of techniques for preventing frequency selective fading. The multicarrier communication enables high speed transmission by transmitting data using a plurality of subcarriers where the transmission speed is suppressed to an extent that no frequency selective fading would occur. Particularly in the OFDM scheme, frequencies of a plurality of subcarriers where data is arranged are orthogonal to each other, and therefore the OFDM scheme has high frequency efficiency among multicarrier communication schemes, and the OFDM scheme can also be implemented in a relatively simple hardware configuration. For this reason, the OFDM scheme is attracting attention as a communication method used for mobile communication based on a cellular scheme, and various studies on the OFDM scheme are underway.
On the other hand, in the cellular scheme, a radio communication mobile station apparatus (hereinafter simply “mobile station”) located near a sector boundary or cell boundary receives large interference from neighboring sectors or neighboring cells, and so the reception performances such as an error rate and throughput deteriorate. Especially, when pilot signals receive such large interference, the reception performances deteriorate significantly.
On the contrary, there is a technique which reduces the influence of interference on pilot signals received from neighboring sectors and improves the reception performances by using pilot signal sequences orthogonal to each other among neighboring sectors (e.g., see Non-Patent Document 1).
Here, the “sector” refers to each of a plurality of areas obtained by dividing an area (i.e., cell) covered by one radio communication base station apparatus (hereinafter simply “base station”), and one base station transmits signals to a plurality of sectors included in one cell with their respective directivities. The same will apply to the following explanations.    Non-Patent Document 1: 3GPP RAN WG1 LTE Adhoc meeting (2005.06) R1-050589